18819917 has 2 divisors, whose sum is σ = 18819918. Its totient is φ = 18819916.

The previous prime is 18819893. The next prime is 18819947. The reversal of 18819917 is 71991881.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17522596 + 1297321 = 4186^2 + 1139^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18819917 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18819947) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9409958 + 9409959.

It is an arithmetic number, because the mean of its divisors is an integer number (9409959).

Almost surely, 2^18819917 is an apocalyptic number.

It is an amenable number.

18819917 is a deficient number, since it is larger than the sum of its proper divisors (1).

18819917 is an equidigital number, since it uses as much as digits as its factorization.

18819917 is an evil number, because the sum of its binary digits is even.

The product of its digits is 36288, while the sum is 44.

The square root of 18819917 is about 4338.1928265120. The cubic root of 18819917 is about 265.9944455847.

The spelling of 18819917 in words is "eighteen million, eight hundred nineteen thousand, nine hundred seventeen".